Key eligibility criteria:

1. Histologically or cytologically confirmed R/R plasmablastic lymphoma
2. Measurable disease, defined as at least one bi-dimensionally measurable nodal lesion, defined as at least 1.5 cm in its longest dimension, or at least one bi-dimensionally measurable extranodal lesion, defined as at least 1.0 cm in its longest dimension
3. At least 1 line of prior therapy, with at least 1 prior line of chemotherapy or radiation
4. At least 18 years old
5. Eastern Cooperative Oncology Group (ECOG) performance status of up to 2 (Karnofsky at least 60%)
6. Adequate organ and marrow function as defined by protocol
7. Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible
8. For patients with evidence of chronic hepatitis B virus (HBV) infection, HBV viral load must be undetectable on suppressive therapy, if indicated
9. Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load
10. Patients with central nervous system (CNS) lymphoma are eligible if they have no CNS-related symptoms at study entry, and Investigator determines that immediate CNS specific treatment is not required and is unlikely to be required during the first cycle of therapy
11. Patients should either have received an autologous transplant or not be a candidate for one
12. Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible
13. Patients with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification. To be eligible, patients should be class II or better
14. Females of child-bearing potential (FCBP) should use effective contraception during treatment with teclistamab and for 6 months after the last dose. FCBP should not breast feed during treatment with teclistamab and for 6 months after the last dose. If pregnancy is suspected or occurs while a FCBP or their partner is participating in this study, they should inform their treating physician immediately. Male patients with a partner who is a FCBP should use effective contraception during treatment and for 3 months after the last dose of teclistamab. FCBP should not donate eggs and men should not donate sperm for the duration of study participation. FCBP should not donate eggs for 6 months and men should not donate sperm for 3 months after completion of the last dose of study drug
15. Vaccination with live virus vaccines is not recommended for at least 4 weeks prior to the start of treatment, during treatment and at least 4 weeks after treatment

1. Patients who have not recovered from adverse events from prior anti-cancer therapy (i.e., residual toxicities greater than Grade 1), exceptions for alopecia and peripheral neuropathy
2. Patients receiving other concurrent investigative treatment
3. History of allergy to compounds similar to study drug
4. Uncontrolled intercurrent illness or other significant health conditions
5. Currently pregnant individuals
6. Patients requiring supplemental oxygen for adequate respiratory function
7. Corticosteroid use besides use for lymphoma control (exceptions defined in protocol)
8. Prior treatment with B-cell maturation antigen therapies
9. Prior treatment with T-cell engager therapies within last 6 months